Cartographers have long struggled with the problem of depicting a
three dimensional object (Earth) on a two-dimensional surface (a
map). One solution is the Topographic Map, or "Topo".
A Topo displays elevations of the ground using contour lines. Contour lines connect points on the earth that have the same elevation. If you find a contour line that is labeled "600" and trace it out, you are following every point on the ground that has an elevation of 600. One important consideration in understanding a Topo is the contour interval. The contour interval tells the difference in elevation between the contour lines. A map with a contour interval of five feet has contour lines that connect elevations at five feet intervals, i.e. 600, 605, 610 etc. A Topographic Map with a contour interval of one foot connects elevations at one foot intervals, i.e. 600, 601, 602 etc.
Four rules to remember about contour lines:
- Contour lines that are closely spaced and parallel indicate steeper slopes.
- Widely spaced contour lines indicate flat terrain.
- Except in the rare cases, contour lines do not cross each other.
- Contour lines in the shape of "V" indicate ditches or streams with the point of the V pointing upstream.
Before requesting a Topographic Map, you should discuss with your Architect or Engineer exactly what information they will need to design your project. That way, there will be no misunderstandings about what the map shows. Lastly, your designer will probably prefer that the map be sent in digital form rather than on paper. This allows your design professional to immediately begin working with the data and is also much more accurate than scaling off a paper map. Of course, we will be happy to plot out a paper copy for you to review as well.